1. Field of the Invention
The present disclosure relates to a control apparatus for induction motor, and more particularly, to a sensor-less vector control apparatus for induction motor including a method for estimating a change in a parameter of an induction motor in real time during sensor-less vector operation.
2. Description of Related Art
Generally, an induction motor includes a stator wound with a winding and a rotor formed by aluminum conductor or iron core. The induction motor is a machine configured to obtain a rotational force by generating a periodic change in current of a winding mounted on a stator, and generating a torque on a rotor according to a constant change in a magnetic field in response to the current change.
In general, a general-purpose inverter is commonly used to drive 3-phase induction motor, and in particular, a general-purpose inverter is commonly used in a variable speed driving field using an induction motor, a hoisting load, or a traction load of an electric vehicle. Operations of an induction motor is generally implemented based on vector control or FOC (Field Oriented Control) algorithm, and a position sensor-less vector control using no position sensor is largely used as a control method for an induction motor in such application fields as where there is a restraint in space or where reduced cost in system is required.
However, among parameters of a squirrel case induction machine, stator resistance and rotor resistance values are changed due to internal electric circuits when a temperature within the induction motor is changed in response to a change in a load and a speed, and an increased temperature of an induction motor leads to change in stator resistance. Vector control commonly used as an induction motor driving method is significantly dependent upon a motor parameter, so fluctuation of the rotor resistance degrades control performance.